10Gbps Optical Receiver and VCSEL Driver in 0.13um CMOS ...

2.2.1 TIA Input Configuration
R D1
i in
C PD
R F
M 2
M 3
M 1
R in
C in
v out
Figure 2.11 Conventional Common-Source TIA
Fig 2.11 shows the conventional common-source TIA. It suffers
from serious design tradeoffs between the transimpedance gain (Z T ) , 3-
dB bandwidth (BW 3-dB ), and photodiode parasitic capacitance (C PD ).
The bandwidth and transimpedance gain of the common-source TIA is
given by:
Z
T
=
A
⋅ R
A + 1
F
≈ R
F
(2.11)
BW
3−dB
≈
2πR
F
A + 1
( C + C
PD
in
)
(2.12)
where A is the open-loop voltage gain of TIA, R F is the feedback
resistance, and C in is the input parasitic capacitance including the ESD
protection diode pad parasitic capacitance and the gate capacitance of
M 1 . For a given C PD , R F is directly proportional to Z T , while is
20